Analgesic and diuretic z-acetylamino



United States Patent ()flice 3,137 ,628 ANALGESIC AND DIURETIC 2-ACETYLAh HNO AND Z-PROPIONYLAMENO M-DIHYDRO-Llt- THIAZENES Werner Meiser, Wuppertal-Vohwinkel, and Hans Henecka, Friedrich Hoifmeister, and Wolfgang Wirth, Wuppertal-Elberfeld, Germany, assignors to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Oct. 23, 1962, Ser. No. 232,577 Claims priority, application Germany Oct. 25, 1961 7 Claims. (Cl. 16765) The present invention relates to novel therapeutic compositions and the administration of those compositions both orally and parenterally, and more especially relates to 2-acylamino-A -dihydro-1,3-thiazines and their nontoxic pharmaceutically acceptable salts in unit dosage form and wherein the essential active therapeutic thiazine derivative is present in an amount ranging from approximately 50 to 100 milligrams per unit dose for preparations in solid form and a 2.5 to 10 percent aqueous injectable solution for preparations in liquid form. The compositions and preparations of the present invention are useful as analgesics and diuretics depending upon the dosage, the administration for diuretic purposes being larger than for analgesic purposes.

The present invention fulfills a need in providing compositions which have moderately strong activity falling between the very potent analgesics such as morphine and the comparatively weak analgesics of the aspirin type.

It has been found, according to the present invention, that acyl derivatives of 2-amino-A -dihydro-1,3-thiazine (also known as Z-amino-penthiazoline-A or, in its tautomeric form, as Z-imino-penthiazoline) having the formula:

wherein R is a methyl or ethyl radical, possess outstanding pharmacodynamic properties. Thus, for example, the acetyl and propionyl compounds have an excellent analgesic effect and, in somewhat highendosages, a diuretic effect.

Compounds of the above ring system have hitherto not been used as medicaments as it has not been known that they have good analgesic and/or diuretic properties.

The monoacetyl-Z-imino-penthiazoline has already been briefly described by Schdberl et al. in Annalen der Chemie, 614, page 95 (1958), whereas the propionyl compound is new. The two compounds are acylamides. It is surprising that, nevertheless, they act as bases which freely dissolve in water with a pH of about 8. Their basicity enables the formation of outstandingly crystalline salts which dissolve in water with a pH of about 4 to 5.5. The salts are very stable, storable compounds, whereas the acetyl and propionyl bases tend to decompose on prolonged storage. This can be explained by the fact that they can be regarded as cyclic isothioureas of which it is known, at least in the open form, that they are not very stable. The acyl bases distill without decomposition at a high vacuum, the acetyl compound being a solid with a melting point of 50 to 53 C. and the propionyl compound being a liquid.

The following non-limitative examples represent typical formulations responding to the present invention.

EXAMPLE I A series of dry ampules, each of which contained Patented June 16, 1964 68.685 milligrams of sterile 2-acetylamino-A -dihydro-1,3- thiazine succinate corresponding to 50 milligrams of active substance per ampule, were emptied and the contents of each ampule was dissolved in 2 milliliters of sterile water to provide a preparation ready for administration.

EXAMPLE II 137.37 grains of 2-acetylamino-A -dihydro-1,3-thiazine succinate corresponding to 100 milligrams of active substance were ground with 40 grams of lactose, 10 grams of talc, 1 gram of magnesium stearate and 111.63 grams of corn starch and compressed into a 300 milligram tablet.

EXAMPLE IV 137.37 grams of Z-acetylamino-A -dihydro-1,3-thiazine succinate was ground with 10 grams of talc, 1 gram of magnesium stearate and 151.63 grams of lactose and compressed into a 300 milligram tablet.

EXAMPLE V Each 60 milligrams of 2-propionylamino-A -dihydro- 1,3-thiazine was dissolved in water and mixed with a solution of 20.55 milligrams of succinic acid in water, sterile filtered, filled into an ampule and freeze-dried. The contents of each ampule were dissolved in 2 milliliters of sterile water to provide a preparation ready for administration.

EXAMPLE VI Each 72.6 milligrams of 2-propionylamino-A -dihydro- 1,3-thiazine hydrochloride corresponding to 60 milligrams of active substance in aqueous solution was sterile filtered, freeze-dried and filled into an ampule. The contents of each ampule were removed and dissolved in 2 milliliters of sterile water to provide a preparation ready for administration.

EXAMPLE VII Each 103 milligrams of 2-acetylamino-A -dihydro-l,3- thiazine succinate corresponding to milligrams of active substance were melted with one of the usual cone or suppository materials and then shaped into cones or suppositories.

In the case of analgesic substances, there are the strongly effective type of compound such as morphine, and the relatively weakly effective type of compound of the pyrazolone-phenacetin-aspirin group. The analgesic efiect of the present compounds lies about half way between these two groups. Due to the high water solubility of the bases, as well as of the salts, any desired pharmaceutical preparations can be prepared, such as tablets, dragees, cones, solutions for parenteral injection, aqueous or alcoholic solutions for peroral application, etc. In the case of solid preparations, it is preferable to use the salts because of their higher melting points. In the case of aqueous preparations, bases or salts can be used, with or without suitable buffering, expediently to a pH of about 6. As single doses of the solid preparations, 25 to milligrams may be considered as the practical range for adults. As injectable solutions, 2.5 to 10 percent aqueous solutions are especially suitable.

Since, in the case of the evaluation of the analgesia tests, it is a question of the registration of reflexes, which 2-ACETYLAMINO-A -DIHYDRO-1,3-THIAZINE (a) Hot Plate Test on the Mouse [Rat Chen, Y. P., and Beckmann, EL, Science, 113, 631 (1951)] In this test, mice are placed on a copper plate heated to 56 C. In this arrangement, untreated animals show an excitation reaction within 8 to 12 seconds (licking of the fore and hind paws). The lengthening of the reaction time to more than 30 seconds is denoted as the analgesic effect. The DE 50 is that close at which 50 percent of the animals exhibit such an extension of the reaction time. The substance was administered subcutaneously; ten animals were used per dose. The DE 50 was 33 trig/kg. Having regard to the LD 50, the therapeutic index is calculated from:

L1) 50 ggs DE50 as (b) Heat Ray Test on the Mouses Tail This test was evolved by Wolf, Hardy and Goodell [1. Clin. Invest. 19, 659 (1940)] for investigation on humans and was modified by Wirth (c. cit.) for animal experiments. Untreated animals react, under the influence of a focused heat ray, by Withdrawing the tail within four seconds. The prolongation of the reaction time to 12 seconds is evaluated as analgesic effect. The substance was here administered subcutaneously or orally, using 10 animals per dose. The subcutaneous DE 50 was 6 mg./ kg. corresponding to a therapeutic index of 23. :In the case of oral administration, the DE 50 was 11 mg./kg., corresponding to a therapeutic index of 45.

( c) Heat Ray Test on the Mouse s Nose [Meiers test; cited by Hotovy, Mercks Jahresbericht LXX, 18, 156/57] If a focused heat ray is directed on the nose of mice, then the untreated animals react within 2 to 3 seconds with defensive movements. After irradiation times of more than seconds, burning occurs.

For the evaluation of the excitation time prolongations, which are used as a measurement of the analgesic effect, the maximum irradiation time of 15 seconds is, fixed as being equal to 100 percent analgesia. The difference between the maximum time ,(15 seconds) and the normal reaction time (2 to 3 seconds) is divided by 10. The number resulting therefrom of 1.2 to 1.3 seconds-depending on the preliminary control-is reckoned at 10 percent analgesia. Accordingly, 50 percent analgesia (:A 50) means, in this test, that of the animals used, on an average, excitation time of 8.5 to 9 seconds is achieved.

The substance was also tested in this test on ten mice per dose, with subcutaneous administration. A 50 was 9 mg./kg., corresponding to a therapeutic index of 16.

(d) Analgesic T est (Pressure Test) on the Rats Paw [Refi Randall and Selitto, Arch. int. PhfllBL, 111, 409 (1947)] In the rat, the pressure sensitivity is tested of a paw edematously modified by the injection of yeast into the planta pedis, Defensive movements of the animal are reckoned as pain reaction. The quantitative measurement of the analgesic effect is carried out by registration of the pressure increase, in mm. Hg, compared with a preliminary control leading to the defensive movement.

L For comparison, besides a paw modified by inflammation, an untreated paw is also tested.

The application of the substance took place subcutaneously, four hours after the injection of the yeast. The analgesia test itself was carried out over a period of three hours.

The increasing of the excitation threshold by mm. Hg, achieved in an average of the animals used, is designated as A100.

For the compound, the inflamed paw gave a A100 value of 20 mg./kg.; therapeutic index:

On the normal paw, we found a A100 value of 25 mg./kg.; therapeutic index=6.

(e) F lexion Test on the Ruhr Hock Modified by Inflammation [Re :La Belle and T'islow, J. Pharm. Exp. Then, 98, 19, 1950] In this test, 02 ml. of a 1 percent silver nitrate solution is injected into the hind hock of rats about eighteen hours before the use of the material to be tested. An acute arthritis develops. Upon flexing the inflamed joint by the experimenter, the animals give a cry of pain. The failure of this reaction under the action of the substance is reckoned as the analgesic effect.

In the case of subcutaneous administration, the DE 50 for the substance was 20 mg./kg.; therapeutic index=7.5.

(f) Tooth Test on the Rabbit [Re'fi Hertle, Schanne and'Staib, Arzneimittel-Forsch., 7, 311 (1957)] In the case of this method, the increasing of the threshold for an electrical stimulus is regarded as a measure of the analgesic effect. The stimulus is given to an in: cisor tooth of the rabbit by way of electrodes.

This method was somewhat modified by us. Instead of the determination of the pain threshold by a short series of individual stimuli, a continuously increasing electrical permanent stimulus was'used with the help of an automatically controlled potentiometer. In this manner, it was possible to obtain a more exact determination of the pain threshold. Technical data: 50 HZ, length of impulse: l0 msec., current density unchanged. Excitation time always up to the pain reaction. Gnawing movements and defensive movements were regarded as pain reactions. As stimulation device, there was used'the neuroten (Siemens-Reiniger). The excitation threshold and threshold increase were measured in ma. Two methods of calculation were usedfor the evaluation:

(1) Average value of the increase of the excitation threshold in ma. in percent of the preliminary control. The increase of the average excitation threshold by 50 percent and by 100 percent is evaluated.

The substance was administered intravenously to ten animals per dose. After the application of 1.6 mg./kg., it came to an average of 50 percent, after 5.6 rug/kg. to 100 percent increase ofthe excitation threshold. The therapeutic index:

Amounts to -1.4 referred to 50% increase of excitation threshold 5 LD 50 Dose for 100% threshold increase threshold increase is achieved by 1.3 mg./kg. and 100% by 2.5 mg./kg. The therapeutic index:

Amounts to -32 LD 50 referred to 50% D f r 100 thr 1 increase of excitation e 0 Increase threshold=6.4

In order to get some idea of the effect of the compound on carnivorous animals, the substance was tested on the cat.

(g) Tail Pressure T est 0n the Cat IRef. Eddy, N. B., J. Pharm. Exp. Then, 45, 339/1932] 2-acetylaminl-N-dihydro-l,3-thiazine subcutaneous:

1. Animal, mg.lkg.=Akg. max.

=2.8 2. Animal, 10 mg.lkg.=Akg. max.

=8.7 3. Animal, mg.lkg.=kg. max.

.0 4. Animal, mg./kg.=Akg. max.

Codeinephosphate subcutaneous:

5. Animal, 5 mg./kg.=Akg. max.

6. Animal, 1O mg.lkg. A kg. max.

7. Animal, 20 mg.lkg.=Akg. max.

Akg. max.=the largest tolerated pressure increase, in kgJcmfl, difference in comparison with the preliminary control in question after application of the substance.

DIURESIS The test is carried out on adult male rats of 140190 g., which had fasted on the evening before the test but had received as much water as desired. Each dose was given to twenty animals. In the next twenty-two hours, the amount of urine excretion was determined.

Increase in Water Excretion in Com. parison with Control in Percent Time In Hours Dose/kg.

per os, 1.58 mg per 05, 15.8 mg

i.v., 1.58 mg":

The compatibility of N-acetylamino-A -dihydro-1,3-thiazine, measured as LD 50 on various animals, is as follows:

Kind of Animal Method of Administration Intravenous days, 5 mg/kg. of the substance in the form of the base, subcutaneously injected. In this time, no effect was observed on the weight, blood constitution, condition of the urine, liver function test (ESP and thymol cloud test).

In the case of one animal, a light tremor was observed about two hours after the first injection, which had disappeared again the next morning. This symptom repeated itself in the same manner up to the 104th injection. In the case of the second animal, it was first ob served after the 19th injection and after the 64th injection faded away.

2-PROPIONYLAMINO-A DIHYDRO-1,3-THIAZINE\ Kind of Animal Method of LD 50, Administration mg./kg.

Mouse Subcutaneous 100 Rat Subcutaneous 155 Rabbit Intravenous 25 The diuretic effect is set out in the following table:

Increase in Water Excre- Tlme in Hours Dose tion in Comparison with Control in Percent 1-6 4.3 mgJkg 30-40. 1-6 l7 mg./kg About 100.

PREPARATION (1) 2-Acetylamino-Penthiazoline and Salts 84 grams of 2-aminopenthiazoline are mixed with milliliters of acetic anhydride. The vigrorous reaction eases off at C. The reaction mixture is subsequently heated on the water bath for fifty minutes. If it is desired to isolate the base, then the reaction mixture is distilled. B.P. 146 C./0.05 mm. Hg. Yield grams. The distillate is stirred with 85 milliliters of absolute ether,

whereupon the Z-acetylamino-penthiazoline crystallized. M.P. 50 C. to 53 C. Yield 90 grams.

If it is desired to isolate the hydrochloride, then the crude acetylation mixture is dissolved in milliliters of absolute alcohol, stirred for one hour with charcoal, filtered off with suction and precipitated with 220 milliliters of ethereal hydrochloric acid, with the addition of milliliters of ethyl acetate. The beautiful crystalline hydrochloride of 2-acetylamino-penthiazoline is washed with ethyl acetate. M.P. 174 C. Yield 114 grams.

The hydrochloride of melting point 174 C. is also obtained when 13 grams of Z-aminopenthiazoline are boiled for thirty minutes with 35 milliliters of acetic anhydride, after treatment with charcoal, filtered off with suction and the salt precipitated out from the filtrate with ethyl acetate, filtered off with suction and washed with dry ether.

53 grams of 2-diacetylamino-penthiazoline (oil of B.P. 137 C./0.2 mm. Hg, produced by peracetylation of 2-amino-penthiazoline with excess acetic anhydride) are dissolved in 105 milliliters of absolute alcohol and mixed, with cooling, with 48 milliliters of ethereal hydrochloric acid. Splitting off of an acetyl residue thereby takes place and the hydrochloride of Z-acetylaminmpenthiazoline is. completely precipitated out by the addition of ethyl acetate. M.P. 174 C. Yield 42 grams.

The hydrobromide of melting point 180 C. is obtained when 98.5 grams of Z-aminopenthiazoline hydrobromide are boiled for thirty minutes with 200 milliliters of acetic anhydride, after treatment with charcoal, filtered off with suction and the crystals obtained filtered off from the filtrate with suction and washed well with dry ether.

39.5 grams of 2-acetylamino-penthiazoline are dissolved in 200 milliliters of ethyl acetate and mixed with 19 grams of tartaric acid in 100 milliliters of absolute alcohol. The tartrate of 2-acetylamino penthiazoline immediately precipitates out and quickly crystallizes completely. The pure white crystals are washed with ethyl acetate. M.P. 139 C. Yield 51 grams.

3.95 grams of 2-acetylamino-penthiazoline are dissolved in 20 milliliters of ethyl acetate and, with ice cooling, mixed with 1.5 grams of succinic acid in milliliters of absolute alcohol. The succinate of Z-aoetylamino-penthiazoline immediately crystallizes out as white crystals. M.P. 145 C. Yield 4.7 grams.

6 grams of 2-diacetylaminopenthiazoline are dissolved in 30 milliliters of ethyl acetate and, with ice cooling, mixed with 2.25 grams of succinic acid in milliliters of absolute alcohol. 2-acetylamino-penthiazoline suc cinate crystallizes out. M.P. 145 C. Yield 5 grams.

3.95 grams of 2-acetylamino-penthiazoline are dissolved in milliliters of ethyl acetate and mixed with 2.45 grams of crystalline phosphoric acid in 10 milliliters of absolute alcohol. Z-acetylamino-penthiazoline phosphate crystallizes out. M.P. 176 C. Yield 6.4

3.95 grams of 2-acetylamino-penthiazoline are dissolved in 20 milliliters of ethyl acetate and, with ice cooling, mixed with 3.3 grams of succinic acid monomethyl ester in '10 milliliters of absolute alcohol. Upon seeding, the methyl ester .succinic'acid salt of 2-acetylamino-penthiazoline of melting point 140 C. crystallizes out as white crystals.

3.95 grants of Z-acetyIairiino pntliiazoline are'diss'olv'ed in 20 milliliters of ethyl acetate and, with ice cooling, mixed with 1.5 grams of "maleic acid in 10 milliliters of absolute alcohol. The maleate of 2-acetylamino-penthiazoline immediately crystallizes out as white crystals of melting point 140 C.

( 2) Z-Propionylamino-Pemhiazoline and Salts 7 goes to 100 (3., and the reaction mixture is subsequently heated for a short time on the water bath. The resulting 2-propionylaminopenthiazoline is distilled. B.P. 153 C./0.25 mm. Hg. Yield 29 grams.

29 grams of propionylamino-penthiazoline are dissolved in milliliters of absolute alcohol and, with ice cooling, precipitated with ethereal hydrochloric acid. The initial crystallization is increased with ethyl acetate and the hydrochloride of 2-propionylamino-penthiazoline is obtained as white crystals of melting point 176 C.

The same hydrochloride is obtained when the crude reaction mixture, without distillation, is mixed With 60 milliliters of absolute alcohol, stirred for one hour with charcoal and, after filtering off of the charcoal with suction, the filtrate precipitated with ethereal hydrochloric acid.

Further salts of Z-acetylaminoand 2-propionylaminopenthiazoline are produced in analogous manner.

What is claimed is:

1. A therapeutic composition consisting essentially of a 2.5 to 10 percent aqueous injectable solution of 2-acetylamino-A -dihydro-lfi-thiazine succinate.

2. A therapeutic composition consisting essentially of a 2.5 to 10 percent aqueous injectablesolution of Z-acetylamino-A -dihydro-l,3-thiazine succinate buffered to a pH of 6 to 7.

3. A medicinal preparation in solid shaped unit dosage form comprising a carrier containing per unit dosage 50 to milligrams of a pharmaceutically acceptable salt of 2-acetylamino-a -dihydro-1,3-thiazine.

4. A method of effecting analgesia and diuresis in patients in need thereof which comprises administering to such patients a therapeutically effective amount of a comosition of claim 1.

patients in need thereof which comprises administering to such patients a therapeutically effective amount of -2- propionylamino-A' -dihydro-1,3-thiazine succinate in a pharmaceutical carrier.

References Cited in the file of this patent FOREIGN PATENTS 752,003 Great Britain July 4, 1956 

1. A THERAPEUTIC COMPOSITION CONSISTING ESSENTIALLY OF A 2.5 TO 10 PERCENT AQUEOUS INJECTABLE SOLUTION OF 2-ACETYLAMINO-A2-DIHYDRO-1,3-THIAZINE SUCCINATE. 